linux-kernel - [PATCH] iio: ssp_sensors: avoid uninitialized variable usage

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Message-Id: <20190322140937.341976-1-arnd@arndb.de>
Date:   Fri, 22 Mar 2019 15:09:22 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     clang-built-linux@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iio: ssp_sensors: avoid uninitialized variable usage

clang points out that 'calculated_time' is only sometimes
initialized here, which leads to incorrect data being
passed into another function:

drivers/iio/common/ssp_sensors/ssp_iio.c:95:6: error: variable 'calculated_time' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
        if (indio_dev->scan_timestamp) {
            ^~~~~~~~~~~~~~~~~~~~~~~~~
drivers/iio/common/ssp_sensors/ssp_iio.c:102:9: note: uninitialized use occurs here
                                                  calculated_time);
                                                  ^~~~~~~~~~~~~~~
drivers/iio/common/ssp_sensors/ssp_iio.c:95:2: note: remove the 'if' if its condition is always true
        if (indio_dev->scan_timestamp) {
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/iio/common/ssp_sensors/ssp_iio.c:84:25: note: initialize the variable 'calculated_time' to silence this warning
        int64_t calculated_time;
                               ^
The data is subsequently ignored by iio_push_to_buffers_with_timestamp(),
but the warning still feels legitimate and to work around it, we can
initialize the time in the other case.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=18501
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/iio/common/ssp_sensors/ssp_iio.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iio/common/ssp_sensors/ssp_iio.c b/drivers/iio/common/ssp_sensors/ssp_iio.c
index 645f2e3975db..81e8f4844c90 100644
--- a/drivers/iio/common/ssp_sensors/ssp_iio.c
+++ b/drivers/iio/common/ssp_sensors/ssp_iio.c
@@ -96,6 +96,8 @@ int ssp_common_process_data(struct iio_dev *indio_dev, void *buf,
 		memcpy(&time, &((char *)buf)[len], SSP_TIME_SIZE);
 		calculated_time =
 			timestamp + (int64_t)le32_to_cpu(time) * 1000000;
+	} else {
+		calculated_time = 0;
 	}
 
 	return iio_push_to_buffers_with_timestamp(indio_dev, spd->buffer,
-- 
2.20.0